Mechanical characteristics and crack propagation mechanism in rectangular and trapezoidal specimens of excavated pillars with various cavities: experimental and numerical investigations
Bibliographic record
Abstract
In this research, the breakage behavior of rock pillars under the uniaxial compressive strength test is investigated using both experimental and three-dimensional discrete element methods. Gypsum samples with rectangular and hourglass hexagonal shapes are constructed to simulate underground mine pillars. Within the samples, various settings of created holes in different angles, numbers, and shape patterns are considered to design a total of 20 configurations for the failure test. Twelve layouts included horizontal rows of 5 holes (1, 2, or 3 rows) at different angles (0°, 30°, 60°, and 90°). The hole patterns in the other 8 arrangements involved some usual geometric shapes including vertical ellipse, vertical rectangle, triangle, horizontal ellipse, horizontal rectangle, diamond, trapezoid, and square. For the experimental tests, 60 specimens are prepared (3 samples for each configuration to increase reliability). For the PFC3D simulations, 20 models with similar setups are prepared to replicate the experiments. The loading rate was set to 0.016 m/s. Our results show that the hole parameters, i.e., angles, numbers, and shape configurations, are the key factors in the failure process. Our analysis helps reveal a correlation between the breakage pattern, the breakage mechanism of discontinuities, and the maximum applied force of the specimens. Increasing the hole angles and numbers add to the total crack number (TCN). The minimum load-carrying capacity of the samples is recorded for the sample with 15 holes at 30° and 60° angles.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".